On Monday, Illinois will become the second state to ban the so-called “gay panic defense” in cases in which a murder defendant tries to justify their violence as a reaction to learning that their victim was gay.

California banned the defense tactic in 2014, a year after the American Bar Association called for its prohibition.

As The Associated Press reports, there is no single standard for the circumstances leading to the defense:

“There are variations, but it generally goes like this: A person doesn’t realize someone is gay or transgender and engages in a flirtation, then discovers that person’s sexual orientation and that discovery triggers a passionate involuntary response such as murder.”

Activists for LGBTQ rights often point to the 1998 case of Matthew Shepard, a 21-year-old college student who was beaten to death by two men, one of whom claimed the victim had made sexual advances towards him.

The activists say they hope the law, which was approved by Illinois lawmakers in May and signed by Gov. Bruce Rauner in August, will provide momentum toward passing similar measures in other states.

“This new law ensures LGBTQ people are not blamed for the violence perpetrated against them simply because of who they are,” Brian C. Johnson, CEO of Equality Illinois, said in a statement shortly after Gov. Rauner signed the law.

The AP adds:

“Supporters plan to revive legislative attempts to ban what’s also known as the ‘trans panic’ defense, in statehouses in Washington and New Jersey, where proposals haven’t yet received committee votes. Advocates also hope to make inroads in New York, Maryland, Michigan, Minnesota and Texas.”

According to a study by the Williams Institute at the University of California Los Angeles Law School, gay panic and trans panic defenses have been used in courts in about half of the states in the U.S., even though no state penal code recognizes it as a free-standing defense.

Some opponents of the ban say that the “gay panic defense” is rarely used and is not a reliable defense argument.

One critic, Cynthia Lee, a law professor at George Washington University law School says the ban may have an unintended consequence:

“Open discussion of pernicious ideas is a better way to deal with such ideas than banning such discussion outright. Along the same lines, banning gay panic arguments from the criminal courtroom is not a good idea because this simply allows bias against homosexuality to fester in the subconscious realm. Open discussion about whether it is reasonable for a heterosexual man to respond to a non-violent homosexual advance with fatal physical violence is a better way to ensure that such bias is mediated by cognitive processes.”

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